Revert some changes made by OOZIE-1341 when a decision is made regarding sharelib related incompatibility

OOZIE-1341 makes the following changes to MapReduceActionExecutor

 try {
            classes.add(Class.forName(STREAMING_MAIN_CLASS_NAME));
        }
        catch (ClassNotFoundException e) {
            log.error("Streaming class not found " +e);
        }

The above blocks eats the exception as test cases related to MapreduceActionExecutor in core cannot find streaming class as the class is in sharelib.
Once the sharelib installation related incompatiblity is fixed, change this accordingly

Also, in MapReduceActionExecutor, the below line is commented. Remove this comment too once a decision is made regarding sharelib

//assertEquals(classes, ae.getLauncherClasses());